| 摘要 |
In the fabrication process of a tube with twin walls, interior (7), exterior (9), they are continuously formed between the cooling nose and two tracks of dies of an extrusion machine carrying the impressions (18) for forming the rings and impressions (18a,18b,18c) in the formation of the sockets. Each impression is connected to atmosphere or to a vacuum source, consistently in operation from the formation of the socket, where the internal wall (7) is submitted to a pressure (Pi) of a value greater than atmospheric, and it requires, during the sockets formation, to modify the value of the pressure (Pm) between the two wall (7,9) in adjusting a value, close to that of the constant interior pressure (Pi), to a value near to the external pressure (Pe) present in the impression.
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